1. Field
This application relates generally to wireless communication and more specifically, but not exclusively, to a multi-mode access point that supports multiple radio access technologies.
2. Introduction
A wireless communication network may be deployed by an operator over a defined geographical area to provide various types of services (e.g., voice, data, multimedia services, etc.) to users within that geographical area. In a typical implementation, macro access points (e.g., each of which corresponds to one or more macrocells) are distributed throughout a network to provide wireless connectivity for access terminals (e.g., cell phones) that are operating within the geographical area served by the operator's network.
A macro network deployment is carefully planned, designed and implemented to offer good coverage over the geographical area. Even with such careful planning, however, such a deployment may not completely accommodate channel characteristics such as path loss, fading, multipath, shadowing, etc., in indoor and potentially other environments. Consequently, macrocell users may face coverage issues (e.g., call outages and quality degradation) indoors and at other locations, resulting in poor user experience.
To supplement conventional network access points (e.g., macrocells) and provide enhanced performance, low-power access points may be deployed to provide coverage for access terminals over relatively small coverage areas. For example, a low-power access point installed in a user's home or in an enterprise environment (e.g., commercial buildings) may provide voice and high speed data service for access terminals supporting cellular radio communication (e.g., CDMA, WCDMA, UMTS, LTE, etc.).
In various implementations, low-power access points may be referred to as, for example, femtocells, femto access points, home NodeBs, home eNodeBs, access point base stations, picocells, etc. In some implementations, such low-power access points are connected to the Internet and the mobile operator's network via a Digital Subscriber Line (DSL), cable internet access, T1/T3, or some other suitable means of connectivity. In addition, a low-power access point may offer typical access point functionality such as, for example, Base Transceiver Station (BTS) technology, a radio network controller, and gateway support node services. While the use of low-power access points helps alleviate coverage issues associated with an operator's network, these types of access points are not widely deployed in many areas.
Moreover, due to network constraints, an operator's network may not effectively support traffic that has a high data rate. For example, through the use of data throttling and/or data usage caps, a wireless network operator may discourage users from accessing high bandwidth applications (e.g., video, downloads, etc.) via a cell phone.
To address these coverage and/or bandwidth constraints, some types of access terminals support multiple modes of operation. For example, an access terminal may support wireless wide area network (WWAN) service (e.g., cellular service) and at least one other type of wireless service (e.g., Wi-Fi). Such a multi-mode access terminal may thus use different wireless services at different times depending on the coverage and/or level of service provided by the different wireless services. For example, a dual-mode cell phone that supports cellular and Wi-Fi service typically defaults to Wi-Fi service whenever Wi-Fi service is available. In this way, the cell phone is able to take advantage of higher peak data rates typically provided by Wi-Fi and, at the same time, reduce load on cellular systems to operators and reduce usage charges (e.g., corresponding to minute and/or data usage) associated with the WWAN service to the users.
Although Wi-Fi service may support higher peak data rates than cellular service, Wi-Fi access may be susceptible to spurious radio interference since Wi-Fi utilizes unlicensed (and, hence, relatively unmanaged) radio spectrum. For example, one source of interference may be in-home interferers such as various consumer electronic devices (e.g. television sets, personal computers, game consoles, etc.) that are Wi-Fi enabled. Another source of interference may be neighborhood interferers such as other Wi-Fi consumer electronic devices deployed in nearby homes, apartments, and other buildings. In general, such sources of interference may degrade Wi-Fi access.
Also, Wi-Fi service may be less predictable than cellular service. For example, as mentioned above, an access terminal (e.g., a smartphone) may always connect to a known Wi-Fi access if it is found. In addition, such an access terminal will typically turn off Wi-Fi access when the display screen of the access terminal is turned-off and instead use a cellular data mode to reduce battery consumption. One rationale for this approach is based on an assumption that the Wi-Fi data rate is only needed when the user is interacting with the access terminal In practice, however, the above approaches are not always the best operational choice. For example, as discussed above, Wi-Fi is subject to significant and unpredictable interference. Hence, automatically selecting Wi-Fi whenever it is present may not always provide the best service for a given user. In addition, the on/off status of the display screen of an access terminal may not provide the best indication of subsequent background/interactive behavior of the access terminal. For example, certain access terminals (e.g. Mirasol-based devices) may have their display screen on all the time. In view of the above, a need exist for more effective scheme for supporting multi-mode access terminals.